1. Field of the Invention
The present invention relates to a traction control device for a vehicle, including wheel brakes mounted on left and right driven wheels, respectively, which are connected to a power source through a differential, and a control unit for operating the wheel brake of the driven wheel which is fallen into an excessively slipping tendency during acceleration of the vehicle.
2. Description of the Prior Art
Such a system is conventionally known, for example, from Japanese Patent Application Laid-open No.222963/88.
In the prior art system, when an excessively slipping tendency is produced in one of the driven wheels during acceleration of the vehicle in a condition where the friction coefficient of the road surface is different between portions on which the left and right driven wheels run, a braking fluid pressure is applied to the wheel brake of the driven wheel fallen into the excessively slipping tendency, so that an actual wheel speed of the driven wheel fallen into the excessively slipping tendency becomes equal to a target wheel speed, and a torque component output as a revolution number to the driven wheel running on the road surface portion of the lower friction coefficient is controlled by braking, in order to provide an effective driving torque to the wheel on the road surface portion of the higher friction coefficient. However, if the brake control causing the wheel speed to become equal to the target value is carried out, the following problems are encountered: a control system is increased in size, and indeterminate transmitting elements are increased. In addition, due to a hysteresis characteristic and various delays, the variations in wheel speeds are increased, or the convergence of the wheel speed is retarded.